Biguanide compounds



Patented Nov. 28, 1950 BIGUANIDE COMPOUNDS Francis Henry Swinden Curd and Francis Leslie Rose, Blackley, Manchester, England, assignors to Imperial Chemical Industries Limited, a corporation of Great Britain N Drawing. Application February 25, 1948,

Serial No. 10,928

2 Claims. 1 This invention relates to new compounds and more particularlyit relates to compounds which are useful as antimalarial agents. The present application is a continuation-in-part of copend- I vention according to which there are provided new biguani'de derivatives of the general formula wherein Z represents a halogen atom of atomic' weight above that of fluorineythat is an atom selected from the group consisting of chlorine,

bromine and iodine; X and Y represent atoms or radicals selected from the group consisting of hydrogen, halogen and lower alkyl (1 to 3 carbon atoms) Q represents the radical of a nitrogenous base selected from the group consisting of monoalkylamines and dialkylamines, provided that the number of carbon atoms contained in Q is more than one and fewer than 8, and R represents an atom'or radical selected from the group consisting of hydrogen and lower alkyl.

Stated in different words, our novel compounds may be defined by the general formula:

R-NC-NH-ICQ I i IL Hv ItH wherein R is a benzenoid hydrocarbon radical carrying at least one and not more than 3 halogen atoms in its meta and para positions, the halogen being preferably one of atomic weight higher than that of fluorine and the ortho-positions of the aryl radical being preferably unsubstituted, while R and Q have themeanings above indicated.

The new biguanide derivatives may be made forexample by the method described in copending application Serial No. 595,892, via, -by..caus-,:

. scribed 2 ing a substituted aryldicyandiamide of the formula:

QN NRCN 2 \H NH wherein X, Y, Z and R have the significance indicated above, to react with a nitrogenous base of the formula QH, wherein Q has the significance given above. The reaction may conveniently be brought about by heating the reagents together, if desired in presenceof a solvent or diluent which for convenience may be an excess of the nitrogenous base QH when this is liquid under the conditions of reaction employed.

The nitrogenous compound QH may be used either in the form of the free base or in the form of a salt for example the hydrochloride. Further the reaction may be advantageously be carried out in the presence of a metal such as zinc or copper which may be used as such or in the form of an oxide, hydroxide, or salt or as a pre-formed addition compound with the amine. There may be used for instance copper powder, hydrated copper oxide, copper sulphate or zinc chloride. In such cases the presence of the metal increases the speed of the reaction and improves the yield of biguanide. Also the biguanide can frequently be conveniently isolated directly from the reaction mixture in the form of a sparingly soluble complex with the metal salt.

The biguanide derivatives of the present invention may also be made by the process dein copending application Serial No. 701,094, viz., by causing a substituted dicyandiamide of the formula:

wherein has the significance given above, to react with an arylamine of the formula wherein X, Y, Z and B have the significance given above. This reaction may conveniently be wherein X, Y, Z and R have the significance given above, with a cyanainide derivative of the formula: QCN, wherein Q has the significance stated above, or by interaction of a guanidine derivative of the formula:

QC-NH2 wherein Q has the significance stated above, with a cyanamide derivative of the formula:

NR-CN wherein X, Y, Z and R have the significance stated above.

These reactionsmay conveniently be effected by heating the reagents together, optionally in the presence of a solvent or diluent. The guanidine derivative may be used in the form of the free base or, if desired, as a salt such as the hydrochloride, carbonate or sulphate. Where the cyanamide is mono-substituted (and hence acidic in nature) it may, if desired, be used in the form of a salt with a base, the guanidine derivative being then used also in the form of a salt. The new compounds of the present invention may.

also be made by the several processes set forth.

in, copending applications Serial Nos. 720,096,

723,450, both now abandoned and 3,816 (of 1948),

now U. S. Patent 2,509,376.

The novel compounds of this invention are all characterised by a common structure, as ex-- pressed by the above general formula, and by substantially common physical andchemical characteristics. Outstanding among their properties is the pharmaceutical property of being excellent antimalarial agents. Our novel compounds constitute synthetic substitutes for quinine of a high order of efiiciency. While the degree of efficacy as to antimalarial agent will, it will be understood, vary from one individual to the next, We have tested so large a number of members of the general class against avian'malaria that it may safely be postulated that all the compounds of the class have good antimalarial properties. Among the numerous compounds actually tested by, us, in avian malaria and found to be effective against both erythrocytic and exoerythrocytic forms of the parasite the followingsubstances may be named.

N -p-chl0rophenyl-N -methyl-N -isopropylbiguanide N -p-chlorophenyl-N -methyl-N -isopropylbiguanide N -m-chlorophenyl-N -isopropylbiguanide N -m-chloropheny1-N -metl1yLN -isopropylbiguanide N -cl1loropheny1-N zN' -diethylbiguanide N -m-chlorophenyl-lW-n-propylbiguanide N -m-cl1lorophenyl-N -ethylbiguanide N -3-cl11oro-4-methylplienyl-N-'-isopropylbiguanide N 3-methyl-4 cl1lor0phenyl-N -isopropylbiguanide N -3 :4-dichlorophenyl-N -isopropylbiguanide N -3 :5-dichlorophenyl-N -is0propylbiguanide1 N -3 :4 :S-trichlorophenyl-N' -isopropylbiguanide N -3 :4 :5trichl0rophenyl-N -n-propylbi'guanide" N -3 :4 :5-trichlor0pl1enyl-N -methyl-N -isopropylbiguanide.- N -p-bromophenyl-N -ethylbiguanide N p-bromophenyl-N -sec.butylbiguanide N -p-br0mopl1enyl-N5-dietl1ylbiguanide la It;

N -p-bromophenyl-N -methybN isopropylbiguanide N -p-brom0phenyl NF'-methyl;N -n-propylbiguanide N -p-bromophenyl-NF-methyl-NP-n-butylbiguanide- N -m-iodophenyl-N -1sopropylblguanide QNHoNHtIJNHPm I it I PrB HNH

N -p-iodophenyl-N -isopropylbiguanide N -p iodophenyl-N -mpropylblguanide N p-i0dophenyl-N -ethylbiguanide N -pi0dophenyl-N -n-butylbiguanide N -p-i0dophenyl-N -methyl-N -is0propylbiguanidev N -p-i0d0pheny1-N -metl1yl-N -n-pr0pylbiguanide N -3 :4-dibromophenyl-N -lsopropylblguanide NE NH Br N -3-brom0-4-chlorophenyl-N isopropylbiguanide N 3-bromo 4-chlorophenyl-N -ethylbiguanide N -3-brom0-4-0lilorophenyl-N -metliyhN -isopropylbiguanide N -3promo-44o(lophenyl-N -isopropylbiguanide N -3Jerome-440dophenyl-N -methylN -isopropylbiguanide,

N -3-iod0-4-chlorophenyl-N -isopropylbiguanide l H. NH Br N -3,-iodorfl-chlorophenyl-N -n-propylbiguanide N -3-iodo-4-chloropl1enyl-N-ethylbiguanide N -3-'iodo4-cl1lorophenyl-N -methyl-n propylbi uanide; N -3-io(lo-Haremophenyl-N -isopropylbiguanide N -3 iodo;4-brom0pl1enyl-N -methyl-n-propylbiguanide N -3 :4-di10doplienyl-N -isopropylbiguanide N -3-chl0ro-4-bromophenyl-Ni-isopropylbiguanide N -3-chloro-4-bromophenyl-N -n-propylbiguanide N -3-chloro-4-bromophenyl N -ethylbiguanide. N -3-chloro-4-bromophenyl-N -methyl-N -isopropylbigllzulide, v N 3-0hlor0-4-b10m0p11enyl-N -methyl-N -n-propylbiguanide N -3-chloro-4-iodophenyl-NF-isopropyllgiguanide N -3-cliloro-4-iodophenyl-N mpropylbiguamde N -3-chloro-4-iodophenyl-N -111ethyl-N -isopropylblguanlde N -3-chlor04-iodophenyl-N -meth yl-N -n-propylbiguamde N -3 :5-dichloro4-bromophenyl-N -1sopropylbiguan1de Br- NHCNEHIJNHPIB NH H 01 Other specific compounds of this invention include: I

N -m-bromophenyl N -methyl-N -isopropylbiguanide N -m-bromophenyl-N -metl1yl-N -n-propylb1guanide N -m-iodophenyl-N -methyl-N -1sopropyllg1gua1 anie N -m-lodophenyl-N -methyl-N -n-propylb1guamde N 3 l-dibromophenyl-N-ethylbi uanlde N -3 :4-dibromophenyl-N -methyl- -n-propylblguanlde N -3-brom0-4-iodophenyl-N-methyl-N -n-propylbiguamde N -3-iodo-4-bromophenyl-N-methy1-Ni-1sopropylblguamde N -3-i0do 4-bromophenyl-N -n-propylblguamde N -3 :4-diiodophenyl-N -methyl-N -n-propylb1guan1de N -3 :4-diiodophenyl-N -n-propylbiguanlde N -3 :5-dichlo1'o-4-bromophenyl-N -ethylbiguamde N -3 :5-dichloro-4-bromophenyl-Nm-propyllnguan de N 4; :5-dichl0ro-4-bromophenyl N methyl N lsopropyl- N -3 bromo 4 methylphenyl N methyl N isOpropylbiguanide N -3-brom04-methylphenyl-N methyl-N -n;propy1b1guamde N -3-bromophenyl-N -methyl-N -isopropylblguanlde N -3-iodophonyl-N -methyl-N -isopropylbiguanide N -3-iodo-4-chlorophenyLN -methyl-N isopropylbiguanide N -Zf bromo 4 methylphenyl N methyl N 7 1sopr0py1- All these substances may be made by one or more of the methods hereinbefore set forth.

The new compounds are strong bases; they form stable salts with organic and inorganic acids which in many cases are freely soluble in water. The saltsmay be made by dissolving the.

biguanides themselves in aqueous solutions of the acid and then evaporating oil. the water, but they are more conveniently obtained in a dry form by mixing the components together in an organic solvent such as for exampleacetone, or an alcohol, in which the salt is sparingly soluble. For use chemotherapeutically it is frequently an advantage to apply the new compounds in the form of their salts, especially those salts which are water-soluble. For this purpose there may be used for example the acetates, propionates, butyrates, crotonates, formates, malonates, succinates, glycollates, tartrates, citrates, hydrochlorides, nitrates, sulphates, lactates, methanesulphonates, methylene disalicylates or the methylene-bis-B-hydroxynaphthoates, or the glycine.

Example 1 19.5 parts of p-chlorophenyl-dicyandiamide,

parts of diethylamine, 140 parts of ethyl alcohol,

and a solution of 12.5 parts of copper sulphate pentahydrate in 60 parts of water are mixed and the mixture is stirred and heated under reflux for 2 hours. The resultant suspension is cooled, diluted with 300 parts of water and filtered. The light-brown solid residue which is mainly the copper complex of Na-p-chlorophenyl-Nw-diethylbiguanide, is dissolved in a mixture of 100 parts of 36% hydrochloric acid and 600 arts of water. A solution of 40 parts of sodium sulphide nonahydrate in 100 parts of water is slowly added. Copper sulphide is precipitated and is filtered off. The clear filtrate is made'strongly alkaline with caustic soda. The precipitate of the crude biguanide so formed is collected, dried and crystallised from petroleum ether. It forms colourless needles which melt at 133-l34 0., uncorr.

In a similar manner, there may be obtained the following biguanides having the melting points indicated.

Example 2 Example 3 Na p chlorophenyl Nw methyl Nw isopropylbiguanide; colourless needles from toluene, M. P. 174-175 C. uncorr.

Example 4 Na-p-chlorophenylNw-ethylbiguanide; colourless prisms from toluene, M. F. 99-10? C.

Ezcample 5 Na-p-chlorophenyl-Nw-n-amylbiguanide; colourless needles from water, M. P. 229 C.

I Example 6 Na-p-chlorophenyl-Na-n-propylbiguanide; colourless crystals from ethanol, M. P. 58.5-6 C.

Example 7 Na .p chlorophenyl-Na-isopropylbiguanide; colourless crystals from aqueous ethanol, M. P. 130-131 0.; the acetate forms colourless crystals from acetone, M. P. 188-189 C.

Example 8 Na p chlorophenyl Nw n butylbiguanide acetate; colourless prisms from acetone, M. P. 158 C.

Example 9 Na-p-chlorophenyl-Na-isobutylbiguanide hydrochloride; colourless plates from acetone, M. P. 232C.

Example 10 Na-p -chlorophenyl-Nw-tert-butylbiguanide hy drochloride; colourless crystals from acetone, M. P. 232-234 C.

Example 11 Nap chlorophenyl-Nw-npropylbiguanide; colourless plates from toluene, M. P. -126 C Example 12 Na p chlorophenyl-Na-methyl-Nw-diethylbiguanide; the hydrochloride crystallises from water in colourless prisms, M. P. 182-484" C.

Ewample 13 A mixture of 1 .6 parts of N -isopropyldicyandiamide and 25 parts of m-chloroaniline hydrochloride dissolved in 250 parts of water is boiled under reflux for 3 hours, The solution is 7 cooled and-crystallisation, i inducedIby-scratch with a glassrod. 'I'he crystals are-filtered; ofi; washed with a little cold water: and then dried. Theyarethen suspended in-50 parts'of acetone, stirred-for:- 10" minutes, :filte'red andwashed with a littleacetone; Recrystallisatidn from water then givesipur'e N -m-chlorophenyl N '-isopropylbiguanide ihydrochlorideiwhich melts at"232 C.

Example 14:

A mixture: of 12.6 .parts .of.N Iisopr.opyldicyandiamide, 19. parts" of N-methyl-p-chloro.

aniline hydrochloride. and. 150 parts .of..water..is

heated under. refluxfor 3 hours. Itis thencooledand the precipitated crystals are-.filteredoil. and washed withalittle water. The driedmaterial. is slurried with. a little ethyl. acetate, filtered, Washed with ethyl. acetate and dried. It is-thenv redissolved in hot water, the solution isaclarified.

by refluxin for minutes. with decolourising carbon, then filtered and allowed to cool and crystallise. There is .thus'obtained- N -p-chlorophenyl-N i-methyl-N isopropylbiguanide3 hydro chloride, which melts at 235-6 C.

Example 1 5 A mixture of .1276 .partsof N -isopropyldicyandiamide, 22' parts of 3:4-dichloroanilinehydro--- chloride and 100 parts of ,li-ethoxyethanol is heated under refluxfor 3 hours. It is then allowedto cooland-the crystals which separate are filtered voff andwashed withz-a little fi-ethoxy.--- ethanol. A further crop of crystals i obtained by the addition of 3 volumes of ethyl acetate to the motherliquon: The total material, thusobtained is dissolved in hotnalcohol, thesolutionis clarified by refluxing for minutes with decolourising carbon, then filteredand allowed to cool and crystallise. There" is thusobtained N 4334- diohlorophenyli- N isopropylbiguanide't-hydro' chloride, which melts at.2l4.-.-5 0.

Example 1 6 A-mixture of 1 J6 parts of N -isopropyldicyandiamide} parts r 0f 3 5dichloroaniline hydro chloride and 100 parts of B-ethoxyetha'nol-"is heated under reflux for. '3. hours. It is then cooled, 200 parts of ethyl acetate are added and the mixture is allowed to stand for lhour; The crystals which separate are filtered ofi and'washedwith a mixture of fi-ethoxyethanol and ethyl acetate: They are then dissolved in =hot-water, the solution is clarified .by refluxing for 10.-.minutes-;with.decolourisingcarbon, thenfilteredand. allowed to cool. The crystals which separate are filtered off, washed and dried.- There is thus obtained N (3:5 dichlorophenyl) N isopropylbiguanider hydrochloride',.iwhich." melts at 239--240- C;

Example 17 A mixture of 12.6 parts of N -isopropyldicyandiamide; 25.6-1oartsof 3 4 5 trichlor'oaniline hydrochloride "and 1 00' parts of water is heated to boiling under reflux. Sufiicient B-ethoxyethanol to bring about complete solution is added and thermixture isboiled'forfihours. Itfis then allowed to cool and f a crop of crystals. separatei This .is filtered. off and-washed" with-aqueous p3 ethoxyethanol. It thendissolved in hot alcohol, the solution is clarified by refluxing for 15 minutes with decolourising carbon, then filtered and: allowed to cool. Thecrystals which'separate are "filtered off; washed and dried; 'lliere is thus. obtained N '(3 24-:5 trichlorophenyD-N iso' propylbiguanide hydrochloride'i which'rmelts I at Exam le 18." p

A mixture of 14 parts of N -methyl-N -isopropyldicyandiamide, 18 parts of m-chloroaniline hydrochloride and 1.50 parts of :water is heated under reflux for minutes, It is then allowed to cool and the crystals which are deposited are filtered-foil; .wasl'ied-.:with :water: and-dried. These are slurried with a little ethyl acetate, then:fil-.

tered offend Washed with ethyl acetate. Theyv are then. dissolved. in hot; water, "thewsolutionis clarified by. refiuxing-y for 10. minutes with decolourising carbon, thenfiltered and allowed itocoolz. The crystals which separate "are filtered ofi; washed: and. driedn There is rthusuobtainedcN m-chlorophenyl N5 methyl Ni isopropylbiguas nide hydrochloride; which melts at 234?. C I

ErampZe IQJ A mixture of=-;4.0'=parts of N :N diethyldicyan diamide, 4,1: parts .of:.m=ch1oroaniline hydroehloride and 10 parts of fi-ethoxyethanol is boiled'un der refiuxffor 30.1"minutes; The: -mixture iscooled, dilutedawith ethyl acetate and' the cryse tallinetsolidis .filt'ered' oif and washed with ethyl." acetate. .It "isc-then dried I and i purified: by crystallisationfrom Water giving;N Fm+chloro=phen yl-N diethylbiguanid'e hydrochloride; M. P. 226

Example :20

To. a solution of 819L3parts "of .3-chlor0-.4-metli.-- ylaniline hydrochloride in 50vparts=of 'fl-ethoxyethanol maintained at the boil: under .refiux. condenser there is .added-6.3 parts of .N3- -iso1oropyldicyandiamidefi After a" few minutes" the. .mix-' ture is cooled, dilutedwwith parts" of ethyl. acetate and. the crystalline. precipitate "isfilte'red ofi, washed 7 witlr ethyl acetate and .dried at 265 C. It is then recrystalised from'water. and N chlorophenyl rN -in-propylbiguanide hydrochlo ride, 228-i229 20: and N -3 4:5-trichlorophenyl-N5lmethylN is0'propylbiguanide hydrochloride; M: R1234 -2359'C. I 7

Example 22 3.66 parts 0f. n-propylaminehydrochloride, 7 .2 parts of m-iodophenyldicyandiamide and 21.5

par-ts ofriitrobenzeneare lieated together'at C'. "for l8i'hours; On' cooling thesemhsolid' mass obtained is "digestedwitli 7% I hydrochloric acid and ether, the mixture 'filteredand the two layers' in the filtrate 'separated.- The acid aqueous solution is madeslightlyalkaline with ammonia and'the solid precipitatediis filtered 01f; washed" with acetone and --or-ystallised from- Water;

1; m iodophe'nyl N n-propylbiuanide' hydrochloride', M. P'."'208-'20'9 *'C. isthusobtained as col-1 ourless prismsa By working in the-manner describedin Exam ple 1 using other-appropriate intermediates, there are obtained the-followingfurther-biguanides.

Example" 23 N -4-chloro 3-bromophenyl;N n-propylbiguas. nid'e-hydrochioride,of MiP; 197 198"'C.

' chloride of M. P. 231-2315 C.

Example 25 N -3-bromo 4 -iodophenyl-N -n-propy1biguanide hydrochloride of M. P. 227-228 C.

Example 26 N -3-bromo 4 iodophenyl-N -ethylbiguanide hydrochloride of M. P. 220221 C.

Example 27 N -3:4--dibromophenyl-N n propylbiguanide hydrochloride of M. P. 217 .5-218 C.

Example 28 N m iodophenyl-N -ethylbiguanide hydrochloride of M. P. 226 -227 C.

Example 29 N -m-bromophenyl-N -ethylbiguanide hydrochloride of M. P. 216-217" C.

Example 30 N -4-chloro-3-bromophenyl-N -ethylbiguanide hydrochloride of M. P. 215-216" C. 1

Example 31 N -4-bromo 3 iodophenyl-N -ethylbiguanide hydrochloride of M. P. 200-201 C.

Example 32 N -4-chloro 3 iodophenyl-N -n-propylbigua nide hydrochloride of M. P. 198-199 C.

Example 33 N -4-chloro-3-bromophenyl N methyl N n-propylbiguanide hydrochloride of M. P. 232- 232.5 C.

Example 34 N -3 :4-dibromophenyl-N -methyl N isopropylbiguanide hydrochloride of M. P. 23l-235 C.

Example 35 N -4-chloro-3-bromophenyl-N -methyl-N -isopropylbiguanide hydrochloride of M. P. 240- 241" C.

Example 36 N -o-bromophenyl-N methyl-N -n-propylbiguanide hydrochloride of M. P. 237 C. 1

Example 37 N -3-chloro-4-iodophenyl N5 methyl-N n propylbiguanide hydrochloride of M. P. 229- 230 C.

Example 38 N -3 :4-diiodophenyl N -methyl-N -isopropylbiguanide hydrochloride of M. P. 235 C.

Example 39 N l-bromo 3 iodophenyl-N -methyl-N -isopropylbiguanide hydrochloride of M. P. 241- Example 40 N -p-iodophenyl-N -methyl e N 11 propylbiguanide hydrochloride of M. P. 238 C. 1

10 Example 42 N 4 chloro 3 iodophenyl-N -methyl-N -npropylbiguanide hydrochloride of M. P. 205 206 C.

Example 43 N -4-ch1or0-3-iodophenyl N methyl-Ni-isopropylbiguanide hydrochloride of M. P. 239- 240 C.

1 Example 44 23 parts of p-bromoaniline are suspended in water and sufficient hydrochloric acid added to give a solution just acid to Congo red. This solution is then diluted to 375 parts with water and 12.6 parts of N -isopropyldicyandiamide are added. ,Themixture is refluxed for '3 hour'sand then allowed to cool. The solid which separates is filtered oil and washed with a little water. Recrystallisation from-water after clarification of the solution with decolourising. charcoal gives a product which has a brownish tinge anda faint odour of p-bromoaniline. It issuspended in a little dry acetone, stirred for 10 minutes, then filtered and washed with a little acetone- A- further recrystallisation from water gives pure N -pbromophenyl N -isopropylbiguanide hydrochloride which melts at 246 C.

Example 45 p A mixture of 12.6,parts of N -isopropyldicyandiamide, 24.3 parts of 3-chlorolebromoaniline hydrochloride and parts of B-ethoxyethanol is heated under reflux for 3 hours. It is then allowed to cool and the crystals which separate are filtered off and washed with a little fi-ethoxyethanol. A further crop of crystals is obtained by the addition of 3 volumes of ethyl acetate to the mother liquor. The total material thus obtained is dissolved in hot alcohol, the solution is clarified by refluxing for 15 minutes with decolourising carbon, then filtered and allowed to cool and crystallise. There is thus obtained N 3 chloro-4-bromopheny1-N -isopropylbiguanide hydrochloride which melts at 226 C.

Example 46 A mixture of 12.6 parts of N -isopropyldicya'ndiamide, 26 parts of p-iodoaniline hydrochloride and 100 parts of c-ethoxyethanol is heated under reflux for 3 hours. It is then cooled, 2010 parts of ethyl acetate are added and the mixture is allowed to stand for 1 hour. The crystals which separate are filtered oil and washed with a mixture of c-ethoxyethanol and ethyl acetate. They are then dissolved in hot water, the solution is clarified by refluxing for 10 minutes with decolourising carbon, then filtered and allowed to cool. The crystals which separate are filtered off, washed and dried. There is thusob'tained N p iodophenyl-N -isopropylbiguanide hydrochloride, which melts at 239 C.

' Example 47 A mixture of 14 parts of N -methyl-N -is'opropyldicyandiamide, 28 parts of p-iodoaniline hydrochloride and 200 parts of. c-ethoxyetlianolis heated under reflux for 1 hour. The mixture is allowed to cool and the crystals which separate are filtered 01f andwashed with a little ,o-ethoxyethanol. They are then dissolved in hot water and the solution is clarified by boiling for 10 minutes with decolourising carbon, then filtered and allowed to cool. The crystals which separate are filtered off, washed and dried. Thereis thus ob- "drochloridefMiP.226 C.

F711 tained N?-p-iodophenylewemethyl N isopropylbiguanide hydrochloride, which melts .at243- 491C.

"Example 48 A mixture of 4.1 .1parts'- of N -ethyldicyandiamide, 8.0 parts of p-bromoaniline hydrochloride -'a"nd 20 parts: of fi-ethoxyethanol is boiled under -r'efiux forl05 minutes; It is then cooled'a'nd' the crystalline solid is filtered oil and dissolved-in dilute hydrochloric:acidf The solution is filtered,

neutralised with ammonia and salted outwith commonmsalt. ".Th'e:N 11:-bromophenyl N ethylibiguanide hydrochloride: thereby precipitated is filtered 01f ja'nd purified 'by crystallisation from waterx It'.has M.'.P.233'-234i C.

By working; in a similar j manner eusingzappro- 1' priat'e intermediate'sthere may also bemade the "following substances "Example-4 9 "Na-m-bromophenyl-Nweisopropylbig uanide hy- =Example 50 Na-p'-bromophenyl-Nw-n propylloiguani'de hydrochloride which-crystallises from water in"'col- "'ourless plates, -M.- P. 221-122? C.

Example 51 Na-p-bromophenyl- N'w -methyl-Nw-isopropylbiguanide mono-hydrochloridewhichz'crystallises -"from' waterin colourless needlesf'M; P; 251C.

Exampleiz biguani'de hydrochloride. M. P. 244 245 C.

. Example 53 f N 3=iodophenyl N -isopropylbiguanidehy'drochloride; M.-P. 246 0.

..Example.-. 54

Example'55 N -4-iodo 3 bromophenyl N isopropylbiguam'dehydrochloride; M-.-.P.3236. C.

- "Example-56 .a.N -3z4-dibromophenyl-nN ,-isopropylbiguan-ide ..-hydrochloride, M. P. 240 C.

I Example 5 7 .,.Nl-4ebromo-3aiodophenyl N .-.isoproy1bigua-1 .--nide hydrochloride, M.P..-239.C.

. Example '58 212 @Example :63

"N .-3.-chloro-4 iodophenyl.- *N ethylbigua-nide hydrochloride, M. P."226-22'l C.

- Example fiei N --3.chloro-l-iodophenyl--'N nide hydrochloride; M. R 225 'C.

Example '65 N m=bromophenyl N rn+propylbiguanide ""hyhydrochloride, M. P, 19 1195 C.

Example '66 N -p-iodophenyleNieethylbiguanide hydrochloride, M. P. 239240 C.

' Example 67 V N -p-iodopheny1 N 5 --.--n-propylbiguanide ;.hydrochloride, M. P. ZZZ-224 Example 68 N -p-iodophenyl-N n+butylbiguanide P chloride, M. P. 207.C.

n-propylbig ua- .h-lldrol'll.6-parts. of pi-bromophen-ylguanide :hydrate and 25 parts of pentanol are mixed, heated to the boil and 15 partsof pentanol distilled from the mixture, 3.9. parts. of. diethylcyanamide are then 7 added-touthe dry-.pentanol solutionof the'gua- TNl-Bti-diio'dophenyl '-jN .isopropylbiguari-ide hydrochloride, M.1P. 237C.

5 lino :Example 559 nide hydrochloride; P. 258 C.

, .Example Example 161 ,N 3echloro-sl-bromophenyl N ethylbigua-- nide-hydrochlorida-M. P.z 2l'l C,

, Example. 62

.. .N .-3 chloro bbromophenyl N n-pr py .gua-nide hydrochloridegilwfil 217: .C.

nidine and the mixture is boiled under refiuxfor 2.5 hours. The reactionmixture is cooled and diluted with 50 parts of benzene and the whole is ,extractediwith'.10;parts of 7% hydrochlor-icracid.

The acid eXtractisma-de alkaline with excess sodium hydroxide solution and filtered. The solid is crystallised from petroleum ether and there is obtained N -pbromopheny1-N :Ni-diethylbiguanide as colourless plates, M. P. -1.41:,C. I

By working in a similar manner and using other appropriate startingmaterials there may be obtained the following further biguanides.

. Example 74 N -'bromophenyleN eisobutylbiguanide; its monohydrochloride crystallises from water in eolourlesspla-tes;M. P.:237-238 C. Y

" Example 75 N p -bromophenyl-N -methyl-N -n-loutylbiguanide; it crystallises from petroleum ether in colourless" plates, M. P. 123-124" C.

Example 76' r N p bromophenyl-N -dimethylbiguanide; it

.crystallises from ethanol in colourless needles,

M. P. 176? C.

13 Example 77 N -p-bromophenyl-N -cye1ohexylbiguanide; it erystallises from benzene in colourless plates, M. P. 181182 0.; its monohydrochloride crystallises from water in colourless needles, M. P. 252-253 C.

While it will be understood that medical utility in the treatment of human malaria may be formally asserted only after extensive clinical trials, it has been found that the efficacy of a substance in avian malaria, particularly in Plasmodium gallinaceum infection of chicks, is a good indication of its utility in the treatment of human malaria. Moreover, efficacy against the exoerythrocytic forms of avian malaria organisms is generally indicative of utility as a causal prophylactic in human malaria. Utility as a causal prophylactic is a very desirable feature of an antimalarial agent and this feature is not possessed by quinine. and, to a degree, clinically prophylactic, these properties being generally indicated by eflicacy against the erythrocytic forms in avian malaria. Thus, the compounds of the present invention possess generally a very important advantage in comparison with quinine. Yet a further advantage presented especially by some of the compounds of the present invention is that we have found that they are effective at a dosage which is much smaller, in relation to the toxic dose than in the case with many pre-existing antimalarial agents.

Quinine is merely curative 5 (w-diethylamino-a-methylbutylamino) -7-methylphenyb -N -isopropylbiguanide.

2. A compound of the general formula:

wherein R is a 1 to 3 carbon atom alkyl radical and alk is a lower alkyl radical.

FRANCIS HENRY SWINDEN CURD. FRANCIS LESLIE ROSE.

REFERENCES CITED The following references are of record in the file of this patent:

Curdet al.: Annals Tropical Med. and Parasitology, vol. 39, December 31, 1945, pp. 208-219.

Spinks et al.: Annals Tropical Med. and Parasitology, vol. 1-39, December 31, 1945, pp. 220-224. 

2. A COMPOUND OF THE GENERAL FORMULA: 